1. Field of the Invention
This invention relates to a downstop slide element usable in a vehicle seat suspension assembly to mount an intermediate frame part for reciprocal sliding movement on a stationary tower part of the seat assembly to compensate for tolerance and wear and to provide for lateral stability.
2. Description of the Related Art
Various types of seat suspension means are known for resiliently supporting a vehicle seat on a vehicle. It is known, for example, to secure a stationary tower frame part on the vehicle. The seat is secured to an intermediate frame part which is mounted for vertical reciprocal movement on the tower frame part by means of interfitting channels, rollers and slides carried by the respective frame parts. A spring suspension is interconnected between the tower and intermediate frame parts to provide floating vertical movement of the seat. Typical patents disclosing this type of seat suspension are U.S. Pat. No. 3,326,603, W. Lehner, issued June 20, 1967; U.S. Pat. No. 3,442,552, W. Lehner, issued May 6, 1969; U.S. Pat. No. 3,572,828, W. Lehner, issued Mar. 30, 1971; and U.S. Pat. No. 3,705,745, M. Ambrosius, issued Dec. 12, 1971.
While such mounting arrangements have been generally satisfactory, they have presented certain problems which have not only increased the cost of manufacture and assembly but have also caused operational and service problems. In seat assemblies of this general type, the seat is supported on the intermediate frame. Lateral stability of the seat, when occupied, that is, its resistance to transverse shifting and rocking when the vehicle goes over uneven ground and shifts the occupant's weight back and forth, depends upon a close tolerance fit between the channels, rollers and slides of the respective stationary and intermediate frame parts. The greater the play, the greater the amount of lateral instability. To solve this problem, the interfitting channels, rollers and slides are manufactured to very close tolerances which minimize lateral play between the two frames as they reciprocate relative to each other. This requires expensive high precision bending and fabrication fixtures and is more labor intensive. If close tolerances are not maintained, play exists and the seat will rock laterally and fatigue the occupant.
Even when close tolerances are maintained with expensive close tolerance manufacture, this lateral stability problem is not solved. During the life of the seat suspension, reciprocation of the intermediate frame relative to the tower frame will take place millions of times, causing wear which creates an ever increasing amount of play between the channels, rollers and slides. This inevitably results in an increase of lateral instability.
The above mentioned patents do not recognize this problem and make no provision for solving it other than by use of expensive close tolerance manufacture. U.S. Pat. Nos. 3,705,745, M. Ambrosius, issued Dec. 12, 1971 and 4,186,963, L. John Koutsky, issued Feb. 5, 1980 both disclose a seat suspension of this general type and recognize the problem of lateral instability. Ambrosius and Koutsky incorporate a third set of transverse rollers and guides in addition to the conventional two pairs of laterally spaced rollers. This third set of roller and roller guide structure adds to the complexity of the seat design and further increases the cost of manufacture and assembly. Close tolerance manufacture is still required and no provision is made to compensate for wear occurring during the operational life of the seat. Therefore, in spite of a high degree of technical development in the seat suspension field over many decades, the need still exists for a way to eliminate the requirements for close tolerance manufacture while providing compensation for manufacturing tolerances and wear in a simple, inexpensive manner to provide a durable rugged seat affording the occupant lateral stability.